The present application claims priority from Japanese Application No. 2001-67617 filed Mar. 9, 2001, the disclosure of which is hereby incorporated by reference herein.
The present invention relates to an electronic device connection cable having a plurality of high-speed signal lines, a plurality of ground lines, and a plurality of low-speed signal lines.
A video game device, an entertainment device, and similar electronic devices are practically used. One of those electronic devices includes a main unit including a central processing unit (CPU) and other electronic components disposed in a case. The electronic device has a controller connected to the main unit and controlled by a user.
Such an electronic device generally uses a storage device such as a flash memory. The storage device is generally provided in the form of a card that can be attached to the main unit of the electronic device.
Advanced electronic devices deal with a large amount of information and need a high-capacity storage device such as a hard disk drive (HDD). One technique to meet the above requirement is to connect a peripheral device serving as an external high-capacity storage device to the electronic device and use it instead of the card-type storage device having only limited storage capacity.
To connect such a peripheral device to the main unit of an electronic device, it is known in the art to use a cable and an interface according to a proper standard such as the ATA (AT Attachment) standard established by the American National Standards Institute (ANSI) or the SCSI (Small Computer System Interface) standard. Another standard for the interface between the main unit of an electronic device and the peripheral device is the UltraATA/66 (UltraDMA/66) standard. The interface according to this standard allows a connection at a rather high speed and at low cost.
In the UltraATA/66 standard, a connector for connecting electronic devices with each other includes 40 pins for data signal lines according to the ATA standard, and a transmission part (cable) includes 40 data signal lines connected to the respective pins and 40 ground lines that are disposed in correspondence with the respective signal lines so as to improve signal quality. The 40 ground lines and 40 data signal lines are alternately disposed in a single flat layer. That is, the cable according to this standard includes a total of 80 signal lines that are all disposed in the single flat layer.
However, in the UltraATA/66 standard, because the transmission part has a flat structure in which all signal lines are disposed parallel to one another in the same single layer, the outward appearance of the transmission part may not be good, and it may not be easy to bend the transmission part when it is connected to an electronic device. Similar problems may also occur in any flat-type cable according to standards other than UltraATA/66.
It is also known in the art to form a transmission part such that each pair of lines is formed by twisting together one data signal line and one ground line, and a plurality of twisted pairs are combined together into a bundle that is circular in cross section. However, in this type of transmission part, some portions of data signal lines are brought into proximity with one another. This may cause crosstalk noise to be generated among data signal lines, and thus this type of transmission part is not used in practical applications in which it is needed to transmit data signals at a high speed. Furthermore, twisting lines makes it difficult to bend the transmission part and thus it is not easy to handle it.
It is an object of the present invention to provide an electronic device connection cable that can transmit data between electronic devices without generating noise and that can be easily handled.
According to an aspect of the present invention, there is provided an electronic device connection cable including a transmission part including a plurality of high-speed signal lines and a plurality of ground lines; and a sheath disposed around the plurality of high-speed signal lines and the plurality of ground lines, wherein the plurality of high-speed signal lines and the plurality of ground lines are arranged such that no interference occurs among signals traveling through the plurality of high-speed signal lines.
Herein, the term xe2x80x9chigh-speed signal linexe2x80x9d refers to a data signal line or the like for transferring data at a high speed in synchronization with a clock frequency to read or write the data. Interference between signals refers to a state in which a signal traveling through a signal line exerts so great an influence on a signal traveling through another signal line that the signal traveling through the another signal line is not transmitted correctly.
In an embodiment according to the invention, the high-speed signal lines and the ground lines are arranged so that no interference occurs among signals transmitted through the high-speed signal lines and noise due to crosstalk among the high-speed signal lines is suppressed to a very low level, thereby ensuring that data is transmitted between electronic devices in a highly reliable fashion.
Furthermore, unlike a flat-type cable that can be bent only along a line in the flat plane of the cable, the electronic device connection cable of the present invention can be easily bent in any desired direction because the electronic device connection cable is disposed within a sheath having the shape of a tube. This makes it possible to easily connect the electronic device connection cable to a device. Herein, the xe2x80x9ctubexe2x80x9d shape refers to a shape that is circular, elliptic, or a polygonal in cross section. Because the transmission part includes no twisted pairs of lines, the transmission part is soft enough to easily bend. This makes it possible to easily handle the transmission part.
Preferably, the transmission part includes a plurality of high-speed signal lines, a plurality of ground lines, and a plurality of low-speed signal lines arranged in a bundle, and the sheath is formed in the shape of a tube within which the bundle of signal lines and ground lines are disposed such that the outer surface of the bundle is covered with the sheath, wherein high-speed signal lines and ground lines are alternately arranged in an outermost layer in the transmission part. Herein, the term xe2x80x9clow-speed signal linexe2x80x9d refers to a data signal line used to transfer data, such as a signal for controlling an access indicator to indicate whether an electronic device is being accessed by another electronic device, at a rather low transfer rate.
In this structure in which high-speed signal lines and ground lines are alternately arranged, any two high-speed signal lines are not arranged at directly adjacent locations, and thus noise due to crosstalk among the high-speed signal lines is suppressed to a very low level, thereby ensuring that data is transferred between electronic devices in a highly reliable fashion. Furthermore, because the high-speed signal lines are disposed in the outermost layer of the transmission part where coupling among high-speed data signal lines is lower than in any other layer, noise due to crosstalk can be suppressed to a lower level than can be achieved when the high-speed signal lines are disposed in an inner layer.
Furthermore, because the sheath is formed so as to have the shape of a tube having no flat surface portion, the transmission part can be easily bent in any desired direction. This results in an improvement in ease of handling.
Preferably, the transmission part includes, in addition to the outermost layer described above, a second layer disposed radially inwardly adjacent to the outermost layer, and a third layer disposed radially inwardly adjacent to the second layer, wherein, in a case where the total number of high-speed signal lines included in the transmission part is greater than the number of high-speed signal lines that can be disposed in the outermost layer, high-speed signal lines that cannot be disposed in the outermost layer are disposed in the third layer such that high-speed signal lines and ground lines are arranged alternately.
In this structure in which the second layer is disposed between the outermost and third layers, because the third layer and the outermost layer are not disposed at directly adjacent locations and because, also in the third layer, high-speed signal lines and ground lines are arranged alternately, any two high-speed signal lines are not arranged at directly adjacent locations and thus noise due to crosstalk among the high-speed signal lines is suppressed to a very low level. Furthermore, because some of the high-speed signal lines are disposed in the third layer, the number of signal lines disposed in the outermost layer can be reduced, and thus the diameter of the transmission part can be reduced. This makes it possible to bend the transmission part more easily. Thus, the transmission part can be handled more easily.
Preferably, the high-speed signal lines include high-speed data signal lines and clock lines; and, in the outermost layer in the transmission part, high-speed data signal lines and ground lines are arranged alternately, wherein in a case in which there are a greater number of high-speed data signal lines than can be disposed in the outermost layer, high-speed data signal lines that cannot be disposed in the outermost layer are disposed in the third layer such that high-speed data signal lines and ground lines are arranged alternately. In this structure, crosstalk noise among the high-speed data signal lines is suppressed to a very low level when data is transferred through the high-speed data signal lines at a high transfer rate. This ensures high reliability in transferring of data.
Preferably, the transmission part includes 18 high-speed signal lines, 20 ground lines, and 22 low-speed signal lines. Herein, the ground lines are used to suppress crosstalk noise among the high-speed signal lines. Therefore, it is not needed to arrange a ground line between low-speed signal lines, because no significant crosstalk noise occurs among low-speed signal lines.
That is, this structure needs only 20 ground lines arranged alternately with the 18 high-speed signal lines. Thus, it is possible to arrange all high-speed signal lines such that any two high-speed signal lines are not located at directly adjacent positions using a minimized total number of signal lines. This makes it possible to form the transmission part so as to have a small diameter.
Preferably, the high-speed signal lines include 16 high-speed data signal lines and 2 clock lines. In this structure, it is possible to parallely transfer respective bits of 16-bit data using the 16 high-speed data signal lines.